The Biotechnology Resource in electron probe microanalysis provides research groups in the Harvard community and nationwide with access to new and complex microanalytical instrumentation and methodologic approaches and trains them in their use. The primary instrument, an electron probe microanalyzer, is capable of localizing any chemical element heavier than boron on a submicron scale, hence within single cells in quantities less than 10 to the minus 15th power grams. It can perform complete elemental analysis on liquid samples of 10 to the minus 10th power liters. A mini computer allows for on line control of the instrument and for a powerful data manipulation. Liquid droplets, isolated cells, biological tissues are now currently analyzed in the Resource. Original results have been obtained in cell, renal, reproductive and digestive physiology and in neuroendocrinology.